Precipitation in Al-Cu-Li alloys: from the kinetics of T1 phase precipitation to microstructure development in friction stir welds

Abstract

Al-Cu-Li based alloys are experiencing a rapid development for aerospace applications. The main hardening phase of this system (T-1-Al2CuLi) forms as thin platelets (1 nm) that can reach diameters of 50 to 100 nm with remarkable stability in temperature. The nucleation, growth and thickening mechanisms of this phase are of crucial importance for the understanding of the microstructures resulting from simple to complex thermo-mechanical treatments, including friction stir welding of such alloys. In this contribution, we present in-situ synchrotron small angle scattering X-ray experiments that enable to better understand the precipitation kinetics and morphology evolution of T-1 precipitates. In a second part, this knowledge is applied to the understanding of the development of FSW microstructures.